Metallization of metal articles by cathode disintegration



y 14, 1940- B. BERGHAUS ET AL. 2.200.909

METALLIZATION OF METAL ARTICLES BY CATHODE DISINTEGRATION Filed Nov. 29, 1938 3 4 VViBurRharok Patented May 14, 1940 UNITED STATES PATENT OFFICE METALLIZATION F METAL ARTICLES BY OATHODE DISINTEGRATION Application November 29, 1938, Serial No. 243,012 In Germany November 30, 1937 1 Claim. (CL 250-275) The invention relates to a method of metallizing metal articles by cathode disintegration, and it consists in this that the metal or metalalloy layer provided by cathode disintegration is wholly or partly diffused into the base metal at high temperature. Preferably, a further metal layer is sprayed on the diffused-in layer at a temperature which lies below the diffusion temperature. The diffusion of the sprayed-on metal layer may be effected in a separate diffusion oven. However, the diffusion may advantageously be effected also during or after the spraying in the cathode disintegration chamber itself. The heating of the metal article to be metallized during the spraying on and the difiusion is preferably efiected by glow current heating in the cathode disintegration chamber. For this purpose the metal articles are connected before and during the metallization permanently or temporarily 2 as a cathode. The cathodic spraying on of the metal articles may also be effected in a reducing gas or gas mixture, such as hydrogen or nitrogen and hydrogen mixture.

The metal layers obtained by this method are exceedingly well adhering and resistant and can cope with the stresses. By preliminarily dusting the article in vacuum an absolutely pure surface is obtained which is freed of traces of oxide. The sprayed-on metal, therefore, comes in direct metallic contact which does not only have a favourable influence on the diffusion of the metals within one another, but in many cases is the reason for it being possible. In contradistinction to electrolytically deposited layers which when thermally treated diffuse-in only here and there and, owing to the metallic contact not being altogether perfect, which is due to enclosures of the electrolyte, generally form bubbles, the surfaces produced by the method according to the 4 invention show a smooth appearance and an equal depth of diffusion.

The method is suitable for the coating and diffusion of metals or alloys into metal articles of any kind for the purpose of increasing the resistance to wear and corrosion and also for increasing their good appearance.

The invention is illustrated diagrammatically, and by way of example, in the accompanying drawing which shows a section through apparatus for the metallization of metal articles by cathode disintegration provided with a device for heating the article by glow current and with a device for subsequent tempering and controlling means associated therewith.

The apparatus illustrated is more particularly disintegration voltage.

intended for the coating of metal articles with metal or alloys by cathode disintegration by means of a source l2 of direct current or a source 22 of alternating current used as a source for the I is the cathode disin- 5 tegration chamber having a cathode 2 to be disintegrated, 3 being the metal article to be coated. The cathode disintegration chamber comprises a lower part 4 and a removable upper part 5. The cathode holder 6 is mounted in an insulated 1. manner in thelower part 4 and is surrounded at a short distance by a screen I. The metal holder 8 of the article is mounted in an insulated manner in the upper part 5 and is surrounded at a short distance by a screen 9, which is conll nected to the positive pole of a source of direct current voltage l2 or a source of rectified current over a switch H), a protective resistance l l and a switch 21. The negative pole of the source of direct current voltage may be connected in the 20 desired succession, on the one hand over the switches 28 and I3 to the cathode holder 6 and on the other hand over the switches 29 and I4 and the regulating resistance l5 to the holder 8 of the article. By means of the regulating resistg5 ance I5 the glow discharge heating current may be adjusted and, according to the invention, the article may be adjusted to any desired temperature which effects the melting and, if desired, the alloying of the sprayed-on material. Further, the 30 screen 9 of the holder 8 may be connected through the conductor I6 and switch I! to the wall of the chamber, or through, the conductor 18 and switch l9 to the screen I of the cathode holder, when required. When a direct current is used 5 switch 30 is open. When a source of alternating current, for instance, a transformer is used as a source of disintegration voltage, the switches.

21, 28 and 29 are opened and the switches l4 and 30 are closed. In this case the screen 9 is connected over the switch I0 and a stop valve 20 for thenegative alternation over a change-over switch 2! to the one pole of a high voltage alternating current transformer 22. The transformer may be connected with its other pole over a changeover switch 23, a regulating resistance I5 and a stop valve 25 for the negative alternation, connected in parallel therewith, to the holder 8 and thus to the article 3, or to a conductor 28 which leads to the screen 9 of the holder 8 over the 50 stop valve 20 for the negative alternation. By means of the change-over switch 2| the one pole of the transformer may be connected to the cathode holder 6 and thus to the cathode 2 to be disintegrated. The individual switches may be op- 58 10 having a metallic cathode therein which comprises, impressing a voltage across the cathode and the article to becoated to create a glow current within the chamber for heating the article and disintegrating metal particles from the cathode onto the article, adjusting said voltage to such a value as to fuse the metal particles into the article being coated, and applying additional metal particles onto coating thus formed at a temperature below the fusion temperature.

BERNHARD BERGHAUS. WILHEIM BURKHARDI'. 

